<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>setInterval</title>
    <style>
      html,
      body,
      section {
        height: 100%;
      }

      section {
        display: flex;
      }

      iframe {
        flex: 1;
        height: 100%;
      }
    </style>
  </head>
  <body>
    <section>
      <iframe src="./page1.html"></iframe>
      <iframe src="./page2.html"></iframe>
    </section>
  </body>
</html>
